May 17, 2007

Technology -- 802.11n instead of B or G?

Nice article describing the differences in the new 802.11n protocol (compared to usual B or G WiFi). Chips first appeared in Macs with Core Duo cpu. The Wi-Fi Alliance released its Draft 2.0 products today. In any case, the relevant point being that with 802.11g we were promised 54 Mbps, yet we probably only really see real through-put of 20-25 Mbps. The n protocol promises us a truly blazing 300 Mbps which being cynics we can rightly assume we won't effectively get. Turns out that's true -- we'll only see 100 Mbps... I think I can deal with that :-)

Inside 802.11n
What you need to know about the wireless networking standard Apple supports

By Glenn Fleishman

Anyone with a yen for disassembling computers—which turns out to be a disturbingly large number of people—discovered last year that Apple had jumped the gun on wireless standards by including Atheros and Broadcom 802.11n, or “N,” chips into some Intel Core 2 Duo models.

This stole some of Apple’s thunder last week at Macworld Expo when it formally announced its adoption of 802.11n and the wireless networking standard’s 100 Mbps-throughput. But what was more surprising was the company’s willingness to commit to a standard that’s a year from completion.
G, I’m having deja vu

Four years ago, Apple also went with a draft of a wireless standard, in that case 802.11g or “G.” at Macworld Expo 2003, and that didn’t seem so bad—did it?

Both G and N come out of the Institute of Electrical and Electronics Engineers, or IEEE—a standards group that brings groups of engineers together to draft and refine protocols. (A third spec, 802.11a, or “A,” uses a different frequency range than B and G, which will become significant later in this article.)

But the G standard was essentially complete in its IEEE task group when Apple shipped the original AirPort Extreme gear. Several firmware upgrades were required to ensure full compliance with the final standard—approved six months later—and interoperability with other companies’ G hardware.

The N chips that Apple put in last year’s machines were based on a much earlier draft of N. That early version, Draft 1.0, has been substantially overhauled, and Draft 2.0 is slated for approval in March. There’s some concern that chips based on Draft 1.0 won’t achieve the full potential of 802.11n when it’s approved in early 2008.

It’s likely Apple received remarkable assurances about future-proofing from its chip partners, and it’s certain we will see many firmware upgrades over time as N develops. And it’s also possible that a network with N devices that all shipped in mid-2007 will outperform a set of 2006-era N devices.
Let N = faster!

The idea behind N is stated in its charter: Enhancements for Higher Throughput. When 802.11g shipped with its “54 Mbps” rated speed, many were disappointed to find that they were lucky to get 20-25 Mbps of real throughput once networking overhead was removed.

The most basic flavor of N shipped by Apple and others has a raw data rate of roughly 300 Mpbs and net throughput of 100 Mbps. This allows N to slightly exceed 100 Mbps Ethernet, still a standard in many offices. While the ratio of 100:300 seems far worse than 25:54, the number to focus on is the real throughput, not the raw data rate. (Tests of early gear by PC World and other labs reveal lots of incompatibilities among equipment, but have seen 100 Mbps throughput with similar equipment in the best cases.)

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